A person who does not file a tax return is eventually audited and then contacted by the IRS and state tax agents.
The willful failure to pay one's taxes is a federal felony.
In some instances the IRS will file the non compliant person's taxes for them based on previous filings and then bill the person for failing to file income tax returns and pay any income taxes that may have been due plus interest and penalties.
In most such case refunds are non existent.
What is the net gain? Either way, that parent gains nothing financially as there is no return. The money remains in government coffers.
what if the noncustodial parent still reside with the custodial parent, is noncustodial parent still obligated to pay childsupport
... have to [pay] child support - yes, until/unless the child is adopted.
Yes. They are still the child's parent and responsible for supporting their child.
Yes, as an adult you can sue a noncustodial parent for back child support. However it is a different story if the noncustodial parent has never been ordered to pay child support. You can still sue them for a percentage of their assets. I am currently working on a case in which my client is sueing his father for 15 years of back child support. Any divorce lawyer can handle this case for you.